JP2018119492A - Piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance cooling efficiency in a piston for internal combustion engine having a cooling passage therein.SOLUTION: A cooling passage inside a piton extends in a direction crossing a movement direction of the piston. A direction from an oil supply port toward an oil discharge port along the cooling passage is a first direction, and a reverse direction to the first direction is a second direction. At least one of the upper surface and lower surface of the cooling passage has a convexo-concave shape. A surface of the convexo-concave shape has a first surface having a component whose normal direction toward the inside of the cooling passage is the first direction, and a second surface having a component whose normal direction is the second direction. An area of the first surface is made larger than an area of the second surface.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a piston for an internal combustion engine. In particular, the present invention relates to a piston for an internal combustion engine having a cooling passage therein.

  Patent Document 1 discloses a piston for an internal combustion engine. A cooling passage (cooling channel) is formed inside the piston. More specifically, an annular cooling passage is formed inside the piston top, and an oil supply passage and an oil discharge passage are provided on the back side of the piston top. A nozzle provided below the piston top part injects oil toward the back side of the piston top part. The injected oil enters the cooling passage through the oil supply passage, passes through the inside of the cooling passage, and is discharged from the oil discharge passage.

JP 2006-200410 A

  One object of the present invention is to provide a technique capable of further enhancing the cooling efficiency of a cooling passage in a piston for an internal combustion engine having a cooling passage inside.

According to the present invention, a piston for an internal combustion engine is provided.
The piston includes a cooling passage formed in the piston and extending in a direction intersecting with the moving direction of the piston.
The cooling passage is
An upper surface which is an inner wall surface on the ascending direction of the piston;
A lower surface that is an inner wall surface of the piston in the downward direction;
An oil supply port for supplying oil to the cooling passage;
And an oil discharge port for discharging oil from the cooling passage.
The direction from the oil supply port to the oil discharge port along the cooling passage is the first direction, and the direction opposite to the first direction is the second direction.
At least a part of at least one of the upper surface and the lower surface of the cooling passage has an uneven shape.
The uneven surface is
A first surface whose normal direction toward the inside of the cooling passage has a component in the first direction;
The normal direction includes a second surface having a component in the second direction.
The area of the first surface is larger than the area of the second surface.

  Consider the oil movement speed in the first direction (direction toward the oil discharge port) in the cooling passage. As the oil movement speed decreases, the movement time until the oil reaches the oil discharge port from the oil supply port increases. If the moving time is long, the oil temperature becomes considerably high before reaching the oil discharge port, and sufficient cooling capacity (heat removal capability) cannot be obtained in the vicinity of the oil discharge port. That is, when the oil moving speed is low, it becomes difficult to realize effective cooling.

  According to the present invention, at least one of the upper surface and the lower surface of the cooling passage has an uneven shape. The uneven surface includes a first surface that faces the first direction (direction toward the oil discharge port) and a second surface that faces the second direction (direction toward the oil supply port). The area of the first surface facing the first direction is larger than the area of the second surface facing the second direction. That is, the first surface facing the first direction is more dominant than the second surface facing the second direction.

  Such an asymmetric uneven shape plays a role of promoting oil movement in the first direction in the cooling passage. Thereby, the oil moving speed in the first direction in the cooling passage is increased, and the time until the oil reaches the oil discharge port is shortened. As a result, an increase in oil temperature until the oil reaches the oil discharge port is suppressed, and a sufficient cooling capacity (heat removal capability) can be obtained in the vicinity of the oil discharge port. That is, the cooling efficiency is improved.

1 is a side view schematically showing a basic configuration of a piston for an internal combustion engine according to an embodiment of the present invention. It is a top view which shows typically the basic composition of the piston for internal combustion engines which concerns on embodiment of this invention. It is the schematic for demonstrating the structural characteristic of the cooling passage of the piston which concerns on the 1st Embodiment of this invention. It is a conceptual diagram for demonstrating the motion of the oil in the cooling passage of the piston which concerns on a comparative example. It is a conceptual diagram for demonstrating the motion of the oil in the cooling passage of the piston which concerns on the 1st Embodiment of this invention. It is the schematic which shows the modification of the cooling passage of the piston which concerns on the 1st Embodiment of this invention. It is a top view for demonstrating the structural characteristic of the cooling passage of the piston which concerns on the 2nd Embodiment of this invention. It is sectional drawing for demonstrating the structural characteristic of the cooling passage of the piston which concerns on the 2nd Embodiment of this invention. It is a top view for demonstrating the structural characteristic of the cooling passage of the piston which concerns on the 3rd Embodiment of this invention. It is sectional drawing for demonstrating the structural characteristic of the cooling passage of the piston which concerns on the 3rd Embodiment of this invention. It is a top view which shows the modification of the cooling passage of the piston which concerns on the 3rd Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

1. Basic Configuration FIG. 1 schematically shows a basic configuration of a piston 1 for an internal combustion engine according to an embodiment of the present invention. The piston 1 reciprocates up and down in a cylinder of the internal combustion engine. Hereinafter, the upward direction and the downward direction of the piston 1 are referred to as “U direction” and “D direction”, respectively. A plane orthogonal to the moving direction (U direction, D direction) of the piston 1 is hereinafter referred to as an “XY plane”.

  A combustion chamber exists on the U direction side of the piston 1, and heat enters the piston 1 from the combustion chamber. In order to cope with such heat input, a cooling passage 10 (cooling channel) for cooling is formed inside the piston 1.

  More specifically, the cooling passage 10 is formed to extend in a direction intersecting with the moving direction (U direction, D direction) of the piston 1. For example, as shown in FIG. 1, the cooling passage 10 is formed inside the top of the piston 1 so as to extend in parallel to the XY plane. The surface on the U direction side of the inner wall surface of the cooling passage 10 is hereinafter referred to as “upper surface 11”. On the other hand, the surface on the D direction side of the inner wall surface of the cooling passage 10 is hereinafter referred to as a “lower surface 12”. The upper surface 11 and the lower surface 12 are opposed to each other.

  An oil supply port 20 and an oil discharge port 30 are formed on the lower surface 12 of the cooling passage 10. The oil supply port 20 is an opening used for supplying oil as a refrigerant into the cooling passage 10. The oil supply passage 21 extends in the D direction from the oil supply port 20 and opens in the D direction on the back surface of the top portion of the piston 1. On the other hand, the oil discharge port 30 is an opening used for discharging oil as a refrigerant from the cooling passage 10 to the outside. The oil discharge passage 31 extends in the D direction from the oil discharge port 30 and opens in the D direction on the back surface of the top portion of the piston 1.

  Below the oil supply passage 21 (D direction), an oil jet device 100 is provided. The oil jet device 100 injects oil toward the oil supply passage 21 of the piston 1. Oil injected from the oil jet device 100 enters the cooling passage 10 through the oil supply passage 21 and the oil supply port 20. The oil that has entered the cooling passage 10 passes through the inside of the cooling passage 10 and is discharged to the outside of the piston 1 through the oil discharge port 30 and the oil discharge passage 31.

  FIG. 2 is an XY plan view schematically showing the basic configuration of the piston 1 viewed from the U direction. In FIG. 2, the oil supply port 20 and the oil discharge port 30 are formed at symmetrical positions across the central axis of the piston 1. The cooling passage 10 is formed in an annular shape so as to connect between the oil supply port 20 and the oil discharge port 30. The annular cooling passage 10 is divided into two semicircular cooling passages 10-1 and 10-2.

  In the piston 1 for an internal combustion engine having the cooling passage 10 as described above, it is desired to further increase the cooling efficiency by the cooling passage 10. In the following, various structural features effective for increasing the cooling efficiency will be described.

2. First Embodiment FIG. 3 is a schematic diagram for explaining the structural features of a cooling passage 10 according to a first embodiment of the present invention. More specifically, FIG. 3 shows a cross-sectional structure along the cooling passage 10 between the oil supply port 20 and the oil discharge port 30. A direction (forward direction) from the oil supply port 20 toward the oil discharge port 30 along the cooling passage 10 is hereinafter referred to as “F direction”. Conversely, the direction (reverse direction) from the oil discharge port 30 toward the oil supply port 20 along the cooling passage 10 is hereinafter referred to as “B direction”. The F direction and the B direction are opposite to each other.

  According to the first embodiment, the lower surface 12 of the cooling passage 10 has the uneven shape 40. In the example shown in FIG. 3, the concavo-convex shape 40 is an asymmetrical “sawtooth shape”. More specifically, the unit structure 50 corresponding to one tooth is repeatedly formed along the F direction. In other words, the plurality of unit structures 50 are continuously formed along the F direction. The surface of such a unit structure 50 (uneven shape 40) corresponds to the lower surface 12 of the cooling passage 10.

  The surface of the unit structure 50 can be divided into two types according to the normal direction. Specifically, as shown in the enlarged view of the unit structure 50 in FIG. 3, the surface of the unit structure 50 includes a first surface 51 and a second surface 52. When the normal direction toward the inside of the cooling passage 10 is considered, the direction of the normal n1 of the first surface 51 has a component in the F direction. On the other hand, the direction of the normal line n2 of the second surface 52 has a component in the B direction. That is, the first surface 51 is a surface facing the F direction, and the second surface 52 is a surface facing the B direction.

  Furthermore, according to the first embodiment, the area of the first surface 51 facing the F direction is larger than the area of the second surface 52 facing the B direction. That is, in the concavo-convex shape 40 of the lower surface 12, the first surface 51 facing the F direction is more dominant than the second surface 52 facing the B direction.

  Hereinafter, effects obtained by the structural features according to the first embodiment will be described. Therefore, first, a comparative example will be described. In the comparative example, it is assumed that the lower surface 12 does not have the uneven shape 40 but has a planar shape.

  FIG. 4 is a conceptual diagram for explaining the movement of oil in the cooling passage 10 in the comparative example. In FIG. 4, an arrow Ain indicates the direction of oil supplied into the cooling passage 10 through the oil supply port 20. An arrow Af indicates the direction (F direction) of the oil that moves due to the force by which the oil is pushed into the cooling passage 10 from the outside. An arrow Ad indicates the oil movement direction (D direction) due to the inertial force when the piston 1 rises in the U direction. An arrow Au indicates the oil movement direction (U direction) due to the inertial force when the piston 1 descends in the D direction.

  Here, the oil moving speed in the F direction in the cooling passage 10 is considered. As the oil movement speed decreases, the movement time (stay time) until the oil reaches the oil discharge port 30 from the oil supply port 20 increases. If the moving time becomes long, the oil temperature becomes considerably high before reaching the oil discharge port 30, and sufficient cooling capacity (heat removal capability) cannot be obtained in the vicinity of the oil discharge port 30. That is, when the oil moving speed is low, it becomes difficult to realize effective cooling. In order to increase the cooling efficiency, it is preferable to increase the oil moving speed in the F direction in the cooling passage 10.

  FIG. 5 is a conceptual diagram for explaining the movement of oil in the cooling passage 10 in the case of the first embodiment. The description overlapping with the comparative example shown in FIG. 4 will be omitted as appropriate. As described above, according to the first embodiment, the lower surface 12 of the cooling passage 10 has the uneven shape 40. Therefore, the arrow Ad has not only the D direction but also a component in a direction intersecting the D direction (F direction, B direction). Similarly, the arrow Au has not only the U direction but also a component in the direction intersecting the U direction (F direction, B direction).

  Furthermore, according to the first embodiment, in the concavo-convex shape 40, the area of the first surface 51 facing the F direction is larger than the area of the second surface 52 facing the B direction. That is, the first surface 51 facing the F direction is more dominant than the second surface 52 facing the B direction. Accordingly, the F direction component is more dominant than the B direction component with respect to the oil movement direction (arrows Au, Ad) due to the inertial force. That the F direction component is larger than the B direction component means that the oil travels in the F direction as a whole.

  Thus, the asymmetric uneven shape 40 according to the first embodiment plays a role of promoting oil movement in the F direction in the cooling passage 10. In the case of the comparative example shown in FIG. 4, only the force by which oil is pushed in from the outside contributes to oil movement in the F direction in the cooling passage 10 (see arrow Af). According to the first embodiment, in addition to that, the asymmetric uneven shape 40 also contributes to oil movement in the F direction in the cooling passage 10. Accordingly, the oil moving speed in the F direction in the cooling passage 10 is higher than in the comparative example, and the time until the oil reaches the oil discharge port 30 is shortened. As a result, an increase in the oil temperature until the oil reaches the oil discharge port 30 is suppressed, and a sufficient cooling capacity (heat removal capability) can be obtained even in the vicinity of the oil discharge port 30. Thereby, cooling efficiency improves.

  FIG. 6 shows a modification of the first embodiment. In the present modification, the upper surface 11 of the cooling passage 10 has an uneven shape 40. The feature of the concavo-convex shape 40 is the same as that shown in FIG. 3, and the area of the first surface 51 facing the F direction is larger than the area of the second surface 52 facing the B direction. Thereby, the same effect as the case of FIG. 3 is acquired.

  Both the upper surface 11 and the lower surface 12 of the cooling passage 10 may have an uneven shape 40. In that case, oil movement in the F direction in the cooling passage 10 is further promoted.

  If at least one of the upper surface 11 and the lower surface 12 of the cooling passage 10 has the uneven shape 40, the effect of the first embodiment can be obtained. Further, it is not necessary that the entire upper surface 11 or the lower surface 12 has the uneven shape 40. If at least a part of the upper surface 11 or the lower surface 12 has the concavo-convex shape 40, the effect of the first embodiment can be obtained.

  Further, the uneven shape 40 is not limited to the “sawtooth shape” as shown in FIG. 3. If the area of the first surface 51 facing the F direction is larger than the area of the second surface 52 facing the B direction, the effect of the first embodiment can be obtained.

3. Second Embodiment Consider an oil inflow rate into the cooling passage 10. The inflow rate is defined by “amount of oil flowing through the cooling passage 10 / amount of oil injected from the oil jet device 100”. The higher the inflow rate, the higher the cooling efficiency.

  One factor that lowers the inflow rate is “external outflow” of oil at the oil supply port 20 of the cooling passage 10. For example, the oil jetted from the oil jet device 100 once enters the cooling passage 10 through the oil supply port 20, but part of the oil bounced off from the upper surface 11 of the cooling passage 10 goes out through the oil supply port 20. It is possible to go. It is also conceivable that the oil once entering the cooling passage 10 goes out through the oil supply port 20 due to the inertial force when the piston 1 is raised.

  In order to increase the inflow rate, it is important to suppress the oil outflow from the oil supply port 20. The second embodiment of the present invention proposes a device for suppressing such external outflow. In addition, the description which overlaps with 1st Embodiment is abbreviate | omitted suitably.

  FIG. 7 is a plan view for explaining the structural features of the cooling passage 10 according to the second embodiment. The format in FIG. 7 is the same as that in FIG. FIG. 8 shows a cross-sectional structure along the line P-P ′ in FIG. 7, and shows structural features at the position of the oil supply port 20 of the cooling passage 10.

  As shown in FIGS. 7 and 8, an annular inlet structure 60 is provided in the vicinity of the oil supply port 20 of the cooling passage 10. More specifically, the inlet structure 60 is formed so as to protrude from the side surface 13 of the cooling passage 10 into the cooling passage 10. Furthermore, the inlet structure 60 is formed so as to approach the upper surface 11 toward the cooling passage 10. That is, the inlet structure 60 has a shape bent from the side surface 13 of the cooling passage 10 toward the upper surface 11.

  Since the inlet structure 60 having such a shape is provided in the vicinity of the oil supply port 20, the oil easily enters the cooling passage 10 at the position of the oil supply port 20, and does not easily come out of the cooling passage 10. That is, the oil outflow from the oil supply port 20 is suppressed. As a result, the inflow rate is improved.

  Further, as shown in FIG. 8, a protrusion 65 may be provided on the upper surface 11 at the position of the oil supply port 20. The oil jetted in the U direction from the oil jet device 100 enters the cooling passage 10 through the oil supply port 20 and strikes the upper surface 11. The protrusion 65 has an effect of dispersing oil hitting the upper surface 11 in the XY plane direction. That is, the protrusion 65 has an effect of suppressing the splash of oil on the upper surface 11. This also contributes to the suppression of the outflow of oil at the oil supply port 20. As a result, the inflow rate is improved.

  An improvement in the inflow rate means that the amount of oil flowing through the cooling passage 10 is increased. Therefore, when the inflow rate is improved, the cooling capacity (heat removal capacity) can be improved over the entire cooling passage 10. Further, in order to increase the amount of oil flowing through the cooling passage 10, it is not necessary to increase the capacity (size) of the oil pump. This is preferable from the viewpoint of reducing the size and cost of the internal combustion engine.

4). Third Embodiment FIG. 9 is a plan view for explaining structural features of a cooling passage 10 according to a third embodiment of the present invention. The format of FIG. 9 is the same as that of FIG. FIG. 10 shows a cross-sectional structure along the line QQ ′ in FIG. The description overlapping with the first embodiment will be omitted as appropriate.

  As shown in FIGS. 9 and 10, the upper surface 11 of the cooling passage 10 has a pleat shape 70 extending along the F direction. In this case, the surface area of the upper surface 11 is larger than when the upper surface 11 is a plane. As the surface area of the upper surface 11 increases, the contact area between the oil as the refrigerant and the upper surface 11 increases. This means that the cooling capacity (heat removal capacity) of the upper surface 11 is increased.

  The upper surface 11 of the cooling passage 10 is a surface close to the combustion chamber (heat generating portion) of the internal combustion engine. According to the third embodiment, since the cooling capacity of the upper surface 11 close to the heat generating portion is increased, more efficient cooling is possible. That is, the cooling efficiency is improved.

  FIG. 11 shows a modification of the third embodiment. The format of FIG. 11 is the same as that of FIG. In this modification, the pleat shape 70 on the upper surface 11 of the cooling passage 10 is formed not in the F direction but in a radial direction orthogonal to the F direction. Even in this case, since the surface area of the upper surface 11 is increased, the same effect can be obtained.

5. Fourth Embodiment It is possible to combine two or more of the first to third embodiments described above. Thereby, a combined effect is obtained.

DESCRIPTION OF SYMBOLS 1 Piston 10, 10-1, 10-2 Cooling channel | path 11 Upper surface 12 Lower surface 13 Side surface 20 Oil supply port 21 Oil supply channel 30 Oil discharge port 31 Oil discharge channel 40 Uneven shape 50 Unit structure 51 First surface 52 Second surface 60 Inlet structure 65 Projection 70 Ridge shape 100 Oil jet device

Claims (1)

A piston for an internal combustion engine,
A cooling passage formed in the piston and extending in a direction intersecting the moving direction of the piston;
The cooling passage is
An upper surface that is an inner wall surface on the rising direction side of the piston;
A lower surface that is an inner wall surface of the piston in the downward direction;
An oil supply port for supplying oil to the cooling passage;
An oil discharge port for discharging oil from the cooling passage,
A direction from the oil supply port toward the oil discharge port along the cooling passage is a first direction, and a direction opposite to the first direction is a second direction,
At least a part of at least one of the upper surface and the lower surface has an uneven shape,
The uneven surface is
A first surface whose normal direction toward the inside of the cooling passage has a component in the first direction;
The normal direction includes a second surface having a component in the second direction;
The area of the first surface is larger than the area of the second surface.

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